Creating a child view controller from a collection view - ios

Question

I am trying to create a child view for my collection view, but whenever I run the app and select a cell from the collection view, nothing appears. How do I fix this so that the tableView is then displayed once a cell is selected?
Here is the code for my collectionView.
import UIKit
class ContentViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {
let imageArray = [UIImage(named: "image 1"), UIImage(named: "image 2"), UIImage(named: "image 3")]
override func viewDidLoad() {
super.viewDidLoad()
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return imageArray.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CustomCell", for: indexPath) as! CustomCell
cell.mapIconImage.image = imageArray[indexPath.row]
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let child = MapItemsViewController()
addChild(child)
view.addSubview(child.view)
child.didMove(toParent: self)
}
class CustomCell: UICollectionViewCell {
#IBOutlet weak var mapIconImage: UIImageView!
}